Image distribution system and client terminal and control method thereof

ABSTRACT

When a viewer resizes an image window while displaying image data distributed from a server on the image window of a client terminal, the client terminal notifies the server of the size of the image window after resizing. The server resizes the image data so that an image has the same size as that of the window, and transmits the resized image data to the client terminal. In this way, the need for the resizing processing in the client terminal can be obviated, thus reducing its load.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an image distribution system whichdistributes image data from a server via a network, a client terminal,and a control method thereof.

2. Description of the Related Art

In recent years, an image distribution system which distributes capturedimage data from a server to a client terminal has prevailed. In such asystem, the server comprises, e.g., a network camera, and the clientterminal comprises a computer. Such an image distribution system is usedespecially for the purpose of surveillance of specific places byutilizing a feature of display images from cameras arranged at aplurality of remote places.

Upon making surveillance based on images, images from a large number ofservers must be simultaneously displayed on a display of the clientterminal. Hence, the images from the servers are respectively displayedin reduced windows on the display. If a particular image is selected,the window of that image can be displayed in an enlarged size. The sizeof the window is changed by enlarging or reducing the window size of anapplication that displays the image. More specifically, a user oftenenlarges or reduces the window size to a desired size by dragging awindow frame displayed by the application with a mouse.

On the other hand, each server transmits captured image data at aresolution which is set in advance to the client terminal. A serverwhich can change this resolution in response to a request from theclient terminal is commercially available. For example, a watcher canselect and set one of resolutions of 640×480 (pixels) and 320×240(pixels) in the server, and can receive and display image data which istransmitted at the set resolution. The resolution in the server can beeasily changed by halving number of pixels to be sampled if thatresolution is ½ the maximum resolution of the image data (see JapanesePatent Laid-Open No. 11-196379).

Therefore, as the resolution provided by the server, a standardresolution, for example, a VGA size (640×480 (pixels)), of a computer orimage media is set as a maximum resolution. Then, the server normallyprovides a QVGA size (320×240 (pixels)) ½ the VGA size, and a QQVGA size(160×120 (pixels)) ½ the QVGA size. However, the following configurationmay also be adopted. That is, an image is captured using ahigh-resolution CCD in advance and an image area according to anarbitrary resolution is transmitted, or when resolution conversion ismade using a high-speed image processing LSI, the resolution of an imageto be transmitted from the server can be changed to an arbitraryresolution other than the prescribed values.

Upon displaying image data distributed from the server on the clientterminal, when the client terminal changes the image window to anarbitrary size, it executes resizing processing for changing therendering size. For example, upon displaying an image which isdistributed from the server and has a resolution of 640×480 (pixels),the size of the window that displays the image is reduced at a clientterminal. In this case, the client terminal executes the resizingprocessing from the resolution of 640×480 (pixels) to that of, e.g.,500×300 (pixels) in accordance with the size of the reduced window.

In such resizing processing at the client terminal, since theinterpolation processing and re-sampling processing between neighboringpixels are executed upon image display, a heavy load is imposed on theprocessing at the client terminal. Especially, when the client terminalconnects a large number of servers and displays a large number of imagesfrom the servers, and when it simultaneously applies resizing processingto these pictures, the load on the client terminal increasessignificantly. Such load increase results in a drop in frame rate upondisplaying an image, and a drop in processing speed of the computer.That is, the load of the resizing processing according to various imagequalities required by the watcher or the operation states of varioussupervising apparatuses used by the watcher cannot be reduced.

Enlarged-scale display by means of the interpolation processing based onneighboring pixels in the client terminal cannot obtain an optimal imagequality according to the window size. For example, when an image windowthat displays image data of 160×120 (pixels) is enlarged to 640×480(pixels), since data before resize is enlarged four times in thevertical and horizontal directions, the image quality deteriorates.

SUMMARY OF THE INVENTION

The object of the present invention is to solve the conventionalproblems.

A characteristic feature of the present invention is to provide an imagedistribution system which can reduce the load of image resizingprocessing on a client terminal, a client terminal, and a control methodthereof.

A characteristic feature of the present invention is to provide an imagedistribution system which can prevent deterioration in quality of animage due to enlargement at a client terminal, a client terminal, and acontrol method thereof.

A characteristic feature of the present invention is to provide an imagedistribution system which allows the user to select a resizing methodcorresponding to the operation states of a client terminal and server,and the operation environment of the system, a client terminal, and acontrol method thereof.

According to the present invention, there is provided an imagedistribution system for transmitting image data captured at apredetermined resolution from a server to a client terminal, anddisplaying the image data on the client terminal, wherein

-   the client terminal comprises:-   a notification unit configured to notify the server of size    information of a window which displays the image data and whose size    has been changed in accordance with a size change instruction; and-   a display control unit configured to control to display the image    data received from the server on the window,-   the server comprises:-   a resizing unit configured to change a resolution upon capturing the    image data based on the size information,-   wherein the display control unit of the client terminal receives the    image data resized by the resizing unit and displays the received    image data on the window.

Further, according to the present invention, there is provided a clientterminal for receiving image data captured at a predetermined resolutionfrom a server, and displaying the received image data on a window,comprising:

-   a notification unit configured to notify the server of size    information of a window which displays the image data and a size of    which has been changed in accordance with a size change instruction;    and-   a display control unit configured to receive the image data resized    by the server, and displaying the resized image data on the window.

Further, according to the present invention, there is provided a methodof controlling an image distribution system for transmitting image datacaptured at a predetermined resolution from a server to a clientterminal, and displaying the image data on the client terminal,comprising:

-   an input step of inputting a change instruction of a size of a    window which displays the image data;-   a notification step of notifying the server of size information of    the window the size of which has been changed in accordance with a    size change instruction;-   a resizing step of changing a resolution upon capturing the image    data based on the size information; and-   a display control step of receiving the image data resized in the    resizing step and displaying the resized image data on the window.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments with reference to theattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate embodiments of the invention and,together with the description, serve to explain the principles of theinvention.

FIG. 1 is a block diagram for explaining the overall system arrangementof an image distribution system according to a first embodiment of thepresent invention;

FIGS. 2A and 2B depict views illustrating windows displayed on a displayof a client terminal according to the first embodiment;

FIG. 3 is a flowchart for explaining the processing in the clientterminal according to the first embodiment of the present invention;

FIGS. 4A and 4B depict views illustrating windows displayed on thedisplay of the client terminal according to a second embodiment;

FIG. 5 is a flowchart showing the processing in the client terminal uponexecuting resizing processing in accordance with the camera controlrights according to the second embodiment of the present invention;

FIGS. 6A and 6B depict views illustrating windows displayed on thedisplay of the client terminal according to a third embodiment;

FIG. 7 is a flowchart showing the processing in the client terminal uponresizing processing of an image according to the third embodiment;

FIG. 8 is a flowchart showing the processing for checking a load on theclient terminal based on an amount L of load calculated using a loadtable;

FIG. 9 depicts an example of a table obtained by numerically convertingthe amounts of load on a client terminal according to the thirdembodiment;

FIG. 10 is a flowchart sowing the load determination processing on theclient terminal using an image frame rate as a checking criterion in amodification of the third embodiment;

FIG. 11 is a flowchart for explaining the resizing processing in animage distribution system according to a fourth embodiment of thepresent invention;

FIG. 12 depicts an example of a table for explaining the relationshipamong the operation mode, the window resize state, and the resizingprocessing according to the fourth embodiment;

FIG. 13 is a flowchart for explaining the resizing processing when animage window is enlarged in an image distribution system according to afifth embodiment; and

FIG. 14 depicts an example of a table for explaining the relationshipbetween the setting items of the client terminal and resizing processingaccording to the fifth embodiment.

DESCRIPTION OF THE EMBODIMENTS

Preferred embodiments of the present invention will now be described indetail with reference to the accompanying drawings. It should be notedthat the embodiments below do not limit the present invention set forthin the claims and that not all of the combinations of features describedin the embodiments are necessarily essential as means for attaining theobjects of the invention.

First Embodiment

The first embodiment of the present invention will be described indetail below with reference to FIGS. 1 to 3.

FIG. 1 is a block diagram for explaining the overall system arrangementof an image distribution system according to the first embodiment of thepresent invention. Building components of the system will be describedfirst.

A server 101 is configured as a network camera used to capture an imageof an object, and distributes an image captured by that camera via anetwork 121. A client terminal 111 is a computer which receives anddisplays image data sent from the server 101. These server 101 andclient terminal 111 are connected to the network 121 such as a LAN, theInternet, or the like. By connecting a plurality of servers 122 to thenetwork 121, the client terminal 111 can simultaneously display aplurality of items of image data from the plurality of servers 122 atremote places on multi-windows and the like. By connecting a pluralityof client terminals 124 to the network 121, image data can bedistributed without limiting viewers. A manager client terminal 123 is amanager of the server 101 that has the camera control rights to be ableto make pan and tilt operations of a panhead of the network camera andvarious settings of the camera.

The server 101 according to this embodiment will be described below.

The server 101 comprises an image sensing unit 102 with a panhead, animage resizing unit 103, an image compressing unit 104, a CPU 105, and acommunication interface (I/F) unit 106. The image sensing unit 102 witha panhead executes pan and tilt drive operations of a panhead inaccordance with control commands from the manager client terminal 123.As a result, the image sensing unit 102 with a panhead can capture animage with a desired angle. The image sensing unit 102 with a panheadreceives these camera control commands from the manager client terminal123 via the CPU 105. The image resizing unit 103 captures image data,and converts the captured image data to a resolution which is set inadvance. That is, resizing of this embodiment includes processing forchanging the resolution (size) of image data. In this embodiment, theresolution of an image provided from the server 101 to the clientterminal includes three different resolutions, i.e., 640×480 (pixels),320×240 (pixels), and 160×120 (pixels). The resolution can be changedaccording to a command from the client terminal, and the image resizingunit 103 receives such change command via the CPU 105. The imagecompressing unit 104 compresses image data of three differentresolutions captured by the image resizing unit 103 in, e.g., a JPEGformat or the like. The CPU 105 converts the three types of compresseddata into a multi-stream. The communication I/F unit 106 distributesthese image data to the client terminals 111 and 124 connected to thenetwork 121.

The client terminal 111 according to this embodiment will be describedbelow. Note that each client terminal 124 has the same arrangement.

The client terminal 111 comprises a communication I/F unit 112, a CPU113, a display 114, and an input unit 115. The input unit 115 is aninput device such as a mouse and keyboard, and is used to control anapplication, to input and transmit control commands to the server 101,and so forth. The communication I/F unit 112 receives the image data ofthe three different resolutions transmitted from the server 101, andsends them to the CPU 113. The CPU 113 decompresses the image data ofthe display resolution set in this client terminal, and displays animage on the display 114 via application software.

FIGS. 2A and 2B illustrate windows displayed on the display 114 of theclient terminal according to this embodiment, and show a state whereinimage data distributed from the server 101 is displayed. Resizing of theimage window will be described below.

FIG. 2A shows the display contents on the display 114 before resizing,and reference numeral 202 denotes a window displayed by the application.On this window 202, reference numeral 203 denotes an image window as anarea for displaying an image. In this case, the client terminal 111receives image data of a resolution of 640×480 (pixels). Hence, thisimage is displayed to have a size of 640 (pixels) in a horizontaldirection 204 and 480 (pixels) in a vertical direction 205. Referencenumeral 206 denotes a tilt-control bar; and reference numeral 207denotes a pan-control bar. By sliding these bars, the pan and tiltangles of the panhead of the image sensing unit 102 with a panhead ofthe server 101 can be remotely controlled. With this control, the clientterminal 111 can view an image obtained by capturing an image of anobject with a desired angle. The client terminal that acquires therights to control a camera can use these camera control tool bars bypressing a control right button 208.

This control right button 208 is enabled when the user selects thisbutton while other client terminals do not acquire the control rights,and is used to limit users so as to inhibit a plurality of clientterminals from simultaneously operating a single camera. Referencenumeral 209 denotes a drag area. When the user drags this area 209 usingthe mouse, he or she can change (resize) the size of the display window202 and image window 203 by the application to an arbitrary size.

FIG. 2B shows the display contents on the display 114 after the size ofthe window 202 is changed by dragging of the mouse using a cursor 220.The image window 203 is resized in accordance with this dragging, asdenoted by reference numeral 212, and is displayed in a reduced size of512 (pixels) in a horizontal direction 213 and 384 (pixels) in avertical direction 214.

As a result of the resize operation of the image window on the clientterminal 111, the image with a size different from the resolution of theimage transmitted from the server 101 must be displayed. For thisreason, the load of re-sampling processing or interpolation processingis imposed on the client terminal 111. In order to reduce such load onthe client terminal 111, it is effective to display an image with thesame size as the resolution of the received image from the server 101.For this purpose, the server 101 must provide image data with aresolution corresponding to the resized window size on the clientterminal 111.

In the first embodiment, in a case that the size of the window to bedisplayed is changed in the client terminal, the client terminal sendsinformation associated with the changed display size to the server 101.Based on this information, the server 101 changes the resolution of acaptured image by the image resizing unit 103 to have a resolutioncorresponding to that display size, and transmits image data whoseresolution is changed in this way to the client terminal. In thismanner, the load of the resizing processing on the client terminal canbe reduced. Further, since the image sensing side (server) executesresizing of an image, deterioration of an image upon resizing can beprevented.

FIG. 3 is a flowchart for explaining the processing in the clientterminal upon executing the resizing processing according to the firstembodiment. FIG. 3 depicts the processing of the client terminal uponexecuting the resizing processing of the window shown in FIG. 2B. Notethat a program which implements this processing is stored in a memory113 a of the CPU 113, and is executed under the control of the CPU 113.

In step S302, the CPU 113 connects the server 101 and receives imagedata of the prescribed resolution. In the first embodiment, the CPU 113receives image data of a resolution of 640×480 (pixels). In step S303,the CPU 113 launches an application to display an image on the imagewindow 203 to have the original resolution (640×480 (pixels)) (FIG. 2A).The CPU 113 determines in step S304 whether or not a user resizes theimage window. If the user resizes the image window, the process advancesto step S305, and the CPU 113 transmits the display size information ofthe image window 212 after resizing to the server 101 via thecommunication I/F unit 112. In the first embodiment, assume that thesize of the image window 212 after resizing is 512 (pixels) in thehorizontal direction×384 (pixels) in the vertical direction, as shown inFIG. 2B.

In this way, the client terminal transmits the display size informationindicating 512×384 (pixels) to the server 101 in step S305. Based onthis received display size information, the server 101 changes the imagesensing size (resolution) from 640×480 (pixels) to 512×384 (pixels), andtransmits image data captured at that resolution to the client terminal111. In step S306, the client terminal 111 displays the received imagestream transmitted from the server 101 as the image data of 512×384(pixels).

As described above, according to the first embodiment, when the displaysize of the image window on the client terminal is changed from, e.g.,640×480 (pixels) to 512×384 (pixels), the client terminal transmits thedisplay size information of the image window after resizing to theserver 101. Based on this information, the server 101 can capture animage at a resolution of 512×384 (pixels), and can transmit the capturedimage data to the client terminal 111. Therefore, upon displaying animage on the client terminal, the need for interpolation processing andre-sampling processing for resizing can be obviated, and the load of theresizing processing on the client terminal can be reduced.

Since the size of the image window on the client terminal corresponds tothe resolution of image data transmitted from the server 101, the imagequality does not suffer any deterioration due to resizing of the displaywindow.

The first embodiment has exemplified the method of dragging the mouse onthe client terminal as the resizing method of the image window. However,the present invention is not limited to this, and various other resizingmethods may be used. For example, resizing based on the numerical valuesof the window size designated from the keyboard, resizing according toprior setting conditions to have a scheduling event, an external sensorevent, or the like as a trigger, and the like may be used.

The first embodiment has explained a case wherein the size of the imagewindow is reduced. However, the present invention is not limited tothis, and can be similarly applied to a case wherein the size of theimage window is enlarged.

Second Embodiment

The second embodiment of the present invention will be described indetail hereinafter with reference to FIGS. 4A and 4B and FIG. 5. Notethat the hardware arrangements of the distribution system, server(network camera), and client terminal are the same as those of the firstembodiment, and a description thereof will be omitted.

FIGS. 4A and 4B illustrate windows displayed on the display 114 of theclient terminal according to the second embodiment. Each of FIGS. 4A and4B simultaneously displays image data at four places distributed fromfour servers. Resizing of the image window will be described below.

FIG. 4A shows the display state on the display 114 before resizing.Reference numeral 402 denotes a window displayed by the application. Onthis window 402, reference numerals 405 to 408 denote image windowswhich respectively display captured images from four servers (notshown). The client terminal according to the second embodiment displaysimage data of a resolution of 320×240 (pixels) distributed from therespective servers. Hence, the size in a horizontal direction 403 ofeach image is 320 (pixels), and that in a vertical direction 404 is 240(pixels). Assume that the client terminal has acquired the cameracontrol rights of, e.g., the third server (image window 407).

Reference numeral 409 denotes a drag area. When a user drags a frame ofthis area 409 using the mouse, the user can change the sizes of thiswindow 402 and the image windows 405 to 408 to arbitrary sizes.

FIG. 4B shows the display contents on the display 114 after the size ofthe window 402 is reduced by dragging the mouse. According to thisoperation, the image windows 405 to 408 are resized (reduced), and eachwindow is displayed to have a size of 200 (pixels) in a horizontaldirection 412×120 (pixels) in a vertical direction 413.

As described above, in order to reduce the load on the resizingprocessing the image window in the client terminal, it is effective togenerate and distribute image data of a resolution corresponding to thesize of the image window by the server 101. However, when a plurality ofclient terminals receive an image from the server 101 and only oneclient terminal takes the liberty to change the image sensing resolutionof the server 101, the following problems are posed. That is, the imagequality of an image displayed on other client terminals that display animage from the server 101 changes, and the display size of the imagewindow of the other client terminals changes unwillingly.

Hence, in order to solve these problems, the second embodiment ischaracterized in that the resizing processing in the server uponresizing of the image window is done in response to only a request fromthe client terminal which has acquired the camera control rights of thatserver. That is, upon resizing the image window shown in FIG. 4A, theclient terminal transmits a resizing command to only the third serverwhose control rights it has acquired, and the client terminal itselfexecutes resizing processing of images from other servers.

Note that a window that displays an image by the resizing processing ofthe server (i.e., an image from the server whose control rights arepossessed by this client terminal) can be expressed clearly to theclient terminal using a bold frame, as denoted by reference numeral 414in FIG. 4B. In this way, a window that allows the resizing processing ofthe server of the plurality of display windows can be clarified, thusproviding convenience in terms of system management such as managementof the load on the client terminal and the like.

FIG. 5 is a flowchart showing the processing in the client terminal uponexecuting the resizing processing in accordance with the camera controlrights according to the second embodiment of the present invention. FIG.5 explains the processing of the client terminal upon execution ofresizing shown in FIG. 4B. Note that a program which implements thisprocessing is stored in the memory 113 a of the CPU 113, and is executedunder the control of the CPU 113.

In step S502, the CPU 113 connects the four servers, and receives imagedata of the prescribed resolution. In the second embodiment, the CPU 113receives image data of a resolution of 320×240 (pixels) distributed fromthe respective servers. The CPU 113 displays images from the respectiveservers on the image window having four areas each having a size thatcan display an image with a resolution of 320×240 (pixels) (FIG. 4A).The CPU 113 determines in step S503 whether or not a user resizes theimage window. If the user resizes the image window, the process advancesto step S504 to confirm if the client terminal has acquired the controlrights of the server (network camera) corresponding to the resized imagewindow. If the client terminal has acquired the control rights of thatserver, the process advances to step S505, and the CPU 113 transmits thedisplay size information of the image window after resizing to theserver (network camera) whose control rights the client terminal hasacquired, i.e., the third server (not shown) in this embodiment.

In FIG. 4B, the size of the image window after resizing is 200 (pixels)in the horizontal direction×120 (pixels) in the vertical direction.Therefore, the CPU 113 transmits the display size information indicating200×120 (pixels) to the third server. The third server changes the imagesensing size in the image resizing unit 103 from 320×240 (pixels) to200×120 (pixels) based on this display size information, and transmitsthat image data to the client terminal 111. In step S506, the clientterminal 111 displays the received image stream transmitted from theserver 101 as the image data of 200×120 (pixels).

On the other hand, for an image from the servers (network cameras) whosecontrol rights the client terminal has not acquired in step S504, theclient terminal itself executes resizing processing of the image fromthe servers and displays it. In the second embodiment, the clientterminal 111 applies rendering processing such as sampling and the liketo images from the servers other than the third server, and displaysthem in a reduced scale.

As described above, according to the second embodiment, upon changingthe display size of the image window in the client terminal, only theclient terminal which has acquired the control rights of the server canrequest resizing processing of an image to that server. Therefore, asituation in which a plurality of client terminals simultaneouslyrequest resizing processing to a single server can be avoided. Uponrequesting the resizing processing from the client terminal to theserver, priority can be given to a specific client terminal, i.e., theclient acquires the control rights of the server.

On the client terminal, since the need for resizing processing for animage from the server whose control rights the client terminal hasacquired can be obviated even when the client terminal displays aplurality of image windows, the processing load for resizing of theimage on the client terminal can be reduced albeit slightly.

Third Embodiment

The third embodiment of the present invention will be describedhereinafter with reference to FIGS. 6A to 10. Note that the hardwarearrangements of the distribution system, server (network camera), andclient terminal are the same as those of the first embodiment, and adescription thereof will be omitted.

FIGS. 6A and 6B illustrate windows displayed on the display 114 of theclient terminal according to the third embodiment. In FIGS. 6A and 6B,the client terminal simultaneously displays image data of threedifferent resolutions distributed from three servers (not shown).Resizing of the image window will be described below.

FIG. 6A shows the display state on the display 114 before resizing.Reference numeral 602 denotes an mage window which displays image dataof a resolution of 320×240 (pixels) transmitted from the first server.Reference numeral 603 denotes an image window which displays image dataof a resolution of 640×480 (pixels) transmitted from the second server.Reference numeral 604 denotes an image window which displays image dataof a resolution of 160×120 (pixels) transmitted from the third server.As described above, these image windows can be resized to arbitrarysizes by, e.g., dragging the mouse.

FIG. 6B shows the display contents on the display 114 after resizing ofeach image window by dragging of the mouse. Reference numeral 605denotes an image window which displays image data after the clientterminal executes the resizing processing of an image of the resolutionof 320×240 (pixels) transmitted from the first server to a size of280×180 (pixels). Likewise, reference numeral 606 denotes an imagewindow which displays image data after the client terminal executes theresizing processing of an image of the resolution of 640×480 (pixels)transmitted from the second server to a size of 600×300 (pixels).Furthermore, reference numeral 607 denotes an image window whichdisplays image data after the client terminal executes the resizingprocessing of an image of the resolution of 160×120 (pixels) transmittedfrom the third server to a size of 220×160 (pixels).

The third embodiment has as its object to reduce the load produced bysuch resizing processing of the client terminal. However, a reduction ofthe load need not be considered for a client terminal which has highprocessing performance with a sufficient margin for the load of theresizing processing. Therefore, whether or not the server executesresizing processing is determined based on the load state of theresizing processing in the client terminal, thus executing processingsuited to the performance of the client terminal.

FIG. 7 is a flowchart showing the processing in the client terminal inthe resizing processing of an image according to the third embodiment.In FIG. 7, whether or not the server executes resizing processing isdetermined based on the amount of load on the processing in the clientterminal. FIG. 7 explains the processing of the client terminal uponresizing the image windows shown in FIG. 6B. Note that a program whichimplements this processing is stored in the memory 113 a of the CPU 113,and is executed under the control of the CPU 113.

In step S702, the CPU 113 connects the three servers, and receives imagedata of the prescribed resolutions. In the third embodiment, the CPU 113receives image data of 320×240 (pixels) from the first server, imagedata of 640×480 (pixels) from the second server, and 160×120 (pixels)from the third server. The CPU 113 then displays images from therespective servers on the image windows to have sizes corresponding tothe respective sizes (FIG. 6A). The CPU 113 determines in step S703whether or not a user resizes the image window. If the user resizes thewindow, the process advances to step S704 to confirm if the load of theresizing processing in the client terminal has a sufficient margin. Ifthe load does not have any sufficient margin, the process advances tostep S705, and the CPU 113 transmits the display size information of theimage window to the server which transmits the image data to be resized.Then, the CPU 113 receives image data which has undergone the resizingprocessing by the server, and displays it on the resized image window instep S706. In this case, since the client terminal transmits the sizeinformation to only the server whose control rights the client terminalhas acquired to make that server execute the resizing processing, theinfluence on other client terminals can be minimized.

On the other hand, if it is determined in step S704 that the load of theresizing processing in the client terminal has a sufficient margin, theprocess advances to step S707, and the client terminal executes theresizing processing of an image and displays the resized image since areduction of the load on the client terminal need not be considered.

The method of determining the load on the resizing processing in theclient terminal (S704) will be described below with reference to FIGS. 8to 10.

The method of determining the load on the client terminal in step S704can be attained using the amount of load on the client terminal, whichis determined based on the image window size and whether or not theclient terminal executes resizing processing. That is, a determiningcriterion is set based on the relationships that the load becomesheavier with increasing display size of the image window, and the loadbecomes heavy in the display size that requires the resizing processingin the client terminal.

FIG. 9 depicts an example of a table which stores the amounts of load onthe client terminal in accordance with the display size. Note that thistable is stored in the aforementioned memory 113 a.

Reference numeral 901 denotes a display size D of an image window of theclient terminal. Reference numeral 902 denotes thenecessity/non-necessity of resizing processing in the client terminal.Since the display sizes (resolution) in the servers are 640×480(pixels), 320×240 (pixels), and 160×120 (pixels), if the display size Dis one of these display sizes, the need for the resizing processing inthe client terminal is obviated (as shown “NOT NECESSARY”). Referencenumeral 903 denotes an amount L of load on the client terminal. In theexample of FIG. 9, when the display size is larger than 640×480(pixels), since it is a nonstandard size, the resizing processing is“necessary”, and the amount L of load assumes a maximum value “64”. Whenthe display size is equal to 640×480 (pixels), since it is a standardsize, the resizing processing is “not necessary”, and the amount L ofload assumes “32” half the above amount of load. When the display sizeis smaller than 640×480 (pixels) and is larger than 320×240 (pixels),since it is a nonstandard size, the resizing processing is “necessary”,and the amount L of load assumes a large value “48”. Likewise, the“necessity/non-necessity” of the resizing processing is determinedaccording to the display size, and the amount L of load is setaccordingly.

FIG. 8 is a flowchart showing the processing for determining the amountof load on the client terminal based on the amount L of load set usingthe table according to the third embodiment. For example, FIG. 8explains the determining method upon execution of resizing shown in FIG.6B. Note that a program which implements this processing is stored inthe memory 113 a of the CPU 113, and is executed under the control ofthe CPU 113.

In step S802, the CPU 113 determines a threshold X used to determine thepresence/absence of a margin for the amount L of load obtained withreference to the table shown in FIG. 9. This threshold X is determinedbased on, e.g., the processing performance of the client terminal. Forexample, since a client terminal, which comprises a high-speed CPU,graphic card, and the like, has high performance with respect to theresizing processing, a large threshold X can be set. In the thirdembodiment, for example, the threshold X=50 is set.

In step S803, the CPU 113 calculates an amount L1 of load beforeresizing. In FIG. 6A of the third embodiment, the client terminaldisplays image windows having three sizes, i.e., 320×240 (pixels),640×480 (pixels), and 160×120 (pixels). Since these sizes are theprescribed display sizes of the servers, no resizing processing on theclient terminal is required. Therefore, the amount L1 of load calculatedbased on the table shown in FIG. 9 is 8+32+2=42. In step S804, the CPU113 compares this amount L1 of load with the threshold X set in stepS802. Since X (=50)>L1 (=42), it is determined that the processing ofthe client terminal has a sufficient margin, and the process advances tostep S805, thus executing the resizing processing in the clientterminal.

In step S805, the CPU 113 calculates an amount L2 of load after theresizing processing. In FIG. 6B of the third embodiment, the clientterminal displays image windows of 280×180 (pixels), 600×300 (pixels),and 220×160 (pixels) after the resizing processing. None of these sizescorrespond to the prescribed resolutions of the servers. For thisreason, the resizing processing in the client terminal is required. Inthis case, the amount L2 of load determined based on the table in FIG. 9is 12+48+12=72. In step S806, the CPU 113 compares this amount L2 (72)of load with the threshold X set in step S802. In this case, since X(=50)<L2 (=72), it is determined that the resizing processing in theclient terminal does not have any sufficient margin. In such case, theCPU 113 notifies the servers of the display size information of thewindows to issue a resizing request for the server.

On the other hand, if the amount L2 of load is smaller than thethreshold X in step S806, it is determined that the resizing processingin this client terminal has a sufficient margin, thus executing theresizing processing by this client terminal.

In the flowchart shown in FIG. 8, a case has been explained wherein theamount L of load is calculated and determined as the determining methodof the client terminal load. However, as another simple determiningmethod, a method using an image frame rate is available.

FIG. 10 is a flowchart for explaining the load determining processing ofthe client terminal to have an image frame rate as a determiningcriterion according to a modification of the third embodiment of thepresent invention. Note that a program which implements this processingis stored in the memory 113 a of the CPU 113, and is executed under thecontrol of the CPU 113.

Referring to FIG. 10, the CPU 113 detects a frame rate value (F1) beforeresizing in step S102. For example, when a client terminal with highprocessing performance receives an image in the NTSC format,F1=30[frames/sec]. The CPU 113 detects a frame rate value (F2) after theimage window is resized in step S103. In step S104, the CPU 113 comparesthe frame rate values before and after resizing of the image window. IfF1=F2, it is determined that the processing of the client terminal has asufficient margin.

On the other hand, if F1>F2 in step S104, since the load on the resizingprocessing of the client terminal becomes heavier, and the decodeperformance and rendering performance of image data have reached limits,a frame rate drop may occur. Therefore, in such case, the CPU 113determines that the processing of the client terminal does not have anysufficient margin, and it notifies the server of display sizeinformation to issue a resizing request for the server.

As described above, according to the third embodiment, when the load onthe processing of the client terminal becomes heavier upon changing thedisplay size of the image window on the client terminal, the resizingprocessing in the server 101 is executed. In this way, appropriateresizing processing according to the processing performance of theclient terminal can be executed.

In the third embodiment, the amount L of load and the frame rate value Fbased on the size of the image window have been exemplified as the loaddetermining criteria on the client terminal. However, the presentinvention is not limited to them. For example, whether or not the useratio of the CPU 113 of the client terminal reaches nearly 100% may beused as a determining condition. Hence, the present invention can beapplied to various other load determining methods of the clientterminal.

Fourth Embodiment

FIG. 11 is a flowchart for explaining the processing for executingresizing processing in an image distribution system according to thefourth embodiment of the present invention. This embodiment will explainthe processing of the client terminal upon resizing the window, as shownin FIG. 2B, in a system which can select two modes, i.e., an imagequality oriented mode and motion oriented mode with respect to thequality of an image. Note that a program which implements thisprocessing and the setting state of the operation mode are stored in thememory 113 a of the CPU 113, and is executed under the control of theCPU 113. Also, since the system and apparatus arrangements according tothe fourth embodiment are the same as those in the first embodimentdescribed above, a description thereof will be omitted.

In step S110, the CPU 113 prompts a user to select one of the imagequality oriented mode and motion oriented mode, and sets the selectedmode. The process advances to step S111, and the CPU 113 connects theserver 101 via the network 121 to receive and display image data of theprescribed resolution. In the fourth embodiment, assume that the clientterminal receives and displays image data of a resolution of, e.g.,640×480 (pixels) (FIG. 2A). The process then advances to step S112 todetermine whether or not a user resizes the image window, as describedabove using FIG. 2B. If it is determined that the user resizes thewindow, the process advances to step S113 to determine whether the userreduces or enlarges the image window.

If it is determined that the user reduces the image window, the processadvances to step S114 to identify the operation mode set in step S110.If the motion oriented mode is set, the process advances to step S116,and the CPU 113 transmits the display size information of the imagewindow 212 after resizing to the server 101 via the communication I/Funit 112. In the fourth embodiment, assume that the window size afterresizing is 512 (pixels) in the horizontal direction×384 (pixels) in thevertical direction, as shown in FIG. 2B above. In this case, the CPU 113transmits the display size information indicating 512×384 (pixels) tothe server 101 in step S116. In this way, the server 101 changes theimage sensing size (resolution) from 640×480 (pixels) to 512×384(pixels) based on the received size information, and transmits thatimage data to the client terminal 111. In step S117, the client terminal111 displays the received image stream transmitted from the server 101as the image data of 512×384 (pixels).

On the other hand, if it is determined in step S114 that the operationmode is the image quality oriented mode, the process advances to stepS118. In step S118, the client terminal 111 resizes data of 640×480(pixels) to that of 512×384 (pixels) by re-sampling processing, anddisplays the resized data.

If the user enlarges the image window from 640×480 (pixels) to, e.g.,700×500 (pixels) in step S113, the process advances to step S115 todetermine the set operation mode. If the operation mode is the motionoriented mode, the process advances to step S118. In step S118, theclient terminal 111 resizes data of 640×480 (pixels) to that of 700×500(pixels) by interpolation processing, and displays the resized data. Onthe other hand, if the operation mode is the image quality oriented modein step S115, the process advances to step S116 as in the above case,and the CPU 113 transmits the display size information indicating700×500 (pixels) to the server 101. In this way, in step S117, theclient terminal 111 receives and displays image data of 700×500 (pixels)which has undergone the resizing processing in the server 101.

As described above, according to the fourth embodiment, whether theserver or client terminal executes the resizing processing can beselected and determined in accordance with the operation mode of theclient terminal and the resizing operation of the window.

FIG. 12 shows an example of the relationship among the operation mode,the window resize state, and the resizing processing according to thefourth embodiment.

In this case, whether or not the server or client terminal performsexecution of resizing processing denoted by reference numeral 1203 canbe selected in accordance with four different conditions of an operationmode 1201 of the client terminal and a resize state 1202 of the imagewindow. Under the four different conditions shown in FIG. 12, theresizing processing is done according to the following reasons.Respective cases 1210-1213 shown in FIG. 12 will be described below.

(1) Case 1210: Upon enlarging the window in the image quality orientedmode, the resolution of image data must be increased in accordance withthe enlarged window size to assure high image quality. Therefore, theserver executes the resizing processing.

(2) Case 1211: Upon reducing the window in the image quality orientedmode, since the resolution of image data is equal to or higher than thereduced window size, image quality can be assured by only re-sampling bythe client terminal. Therefore, the client terminal executes theresizing processing.

(3) Case 1212: Upon enlarging the window in the motion oriented mode,the data size must not be increased so as to prevent a frame rate dropresulting from a limitation of a line transmission capacity. Therefore,the client terminal executes the resizing processing.

(4) Case 1213: Upon reducing the window in the motion oriented mode, thedata size is reduced by setting the same resolution as that of thereduced window size, thus assuring a frame rate. Therefore, the serverexecutes the resizing processing.

Note that the fourth embodiment has exemplified combinations of theimage quality oriented mode and motion oriented mode as the conditionsof the operation modes, and enlargement and reduction of the window.However, the present invention is not limited to this. For example,whether the client terminal or server executes resizing processing maybe determined to have, e.g., a scheduling event or external sensor eventas a trigger.

Fifth Embodiment

The fifth embodiment of the present invention will be describedhereinafter with reference to FIGS. 13 and 14. Since the system andapparatus arrangements according to the fifth embodiment are the same asthose in the above embodiments, a description thereof will be omitted.

As has been described in the above embodiments, upon changing the sizeof the window to be displayed on the client terminal 111 underpredetermined conditions, the client terminal 111 transmits informationassociated with the changed display size to the server 101. Based onthis information, the server 101 changes the resolution of an image tobe captured by the image resizing unit 103 to have a resolutionaccording to the display size, and transmits image data whose resolutionhas been changed to the client terminal 111. In this way, the load ofthe resizing processing on the client terminal 111 can be reduced.

On the other hand, the amount of image data changes after the resizingprocessing in the server 101 according to the window size. If the amountof image data increases, it may exceed the allowable amount of data ofthat line depending on the network involved, or it may occupy most ofthe allowable amount of data of the line. To solve such problem, uponchanging the window size on the client terminal 111, whether the clientterminal 111 or the server 101 executes resizing processing is selectedin accordance with the line transmission capacity and line quality used,thus allowing resizing processing suited to the system environment.

FIG. 13 is a flowchart for explaining resizing processing upon enlargingthe image window in an image distribution system according to the fifthembodiment. Note that a program which implements this processing and thesetting state of the operation mode are stored in the memory 113 a ofthe CPU 113, and is executed under the control of the CPU 113. Also,since the system and apparatus arrangements according to the fifthembodiment are the same as those in the first embodiment describedabove, a description thereof will be omitted. The following descriptionwill be given for a system which can select two lines including FTTHconnection, i.e., a large-capacity line, and PPP connection, i.e., asmall-capacity line as the types of lines.

In step S130, a user selects and sets one of the FTTH connection and PPPconnection. In step S131, the CPU 113 connects the server 101 via thenetwork 121, and receives and displays image data of the prescribedresolution. In the fifth embodiment, assume that the client terminalreceives and displays image data of a resolution of, e.g., 640×480(pixels) (FIG. 2A). The process then advances to step S132 to determinewhether the user enlarges the image window on the client terminal 111.If the user enlarges the window, the process advances to step S133 todetermine the set line type. If the FTTH connection, i.e., thelarge-capacity line is set, the process advances to step S134, and theCPU 113 transmits the display size information of the enlarged imagewindow to the server 101 via the communication I/F unit 112.

In the fifth embodiment, assume that the window size after resizing is,e.g., 1920 (pixels) in the horizontal direction×1080 (pixels) in thevertical direction.

In this way, in step S134 the CPU 113 transmits the display sizeinformation indicating 1920×1080 (pixels) to the server 101. Based onthe received display size information, the server 101 changes the imagesensing size (resolution) from 640×480 (pixels) to 1920×1080 (pixels),and transmits image data captured using the changed size to the clientterminal 111. The process then advances to step S135, and the clientterminal 111 displays the received image stream transmitted from theserver 101 as the image data of 1920×1080 (pixels).

On the other hand, if the line type is the PPP connection, i.e., thesmall-capacity line in step S133, the process advances to step S136. Instep S136, the client terminal 111 resizes data of 640×480 (pixels) tothat of 1920×1080 (pixels) by interpolation processing, and displays theresized data.

As described above, according to the fifth embodiment, upon enlargingthe window in case of the small-capacity line, the client terminalexecutes resizing processing so as to prevent the amount of image datatransmitted through the line from increasing. In this way, appropriateresizing processing according to the line transmission capacity can bedone.

Note that the fifth embodiment has exemplified the line types as settingitems of the client terminal. However, the present invention is notlimited to this.

FIG. 14 shows an example of the relationship between the setting itemsof the client terminal and the resizing processing.

In the aforementioned fifth embodiment, whether the client terminal 111or server 101 executes resizing processing is determined according to aline condition 1401. Like in the line condition 1401, whether the clientterminal 111 or server 101 executes resizing processing can bedetermined according to the following conditions.

(1) “Performance” 1402 is an item example associated with the operationperformance of the client terminal 111. When the client terminal 111 isin a power saving mode, the server 101 executes resizing processing toreduce the load on the resizing processing in the client terminal 111.

(2) “Model” 1403 is an item example associated with the model of theclient terminal 111. When the client terminal 111 is a cellular phone,since it has low processing performance, the server 101 executesresizing processing.

(3) “Function” 1404 is an item example associated with the applicationfunction of the client terminal 111. When the client terminal 111 isrecording an image, since the load on the client terminal 111 becomesheavier, the server 101 executes resizing processing.

(4) “Quality” 1405 is an item example associated with the quality of animage to be displayed on the client terminal 111. When the clientterminal 111 requires a high-quality image, since an image with the sameresolution as that of the image window is required, the server 101executes resizing processing.

The conditions that the watcher can be set, and the environmentalconditions of a supervising system are not limited to such specificconditions. Whether the client terminal or server executes resizingprocessing may be determined to have a scheduling event or externalsensor event as a trigger. In this way, the example of the presentinvention can be applied to various other conditions. The supervisingsystem has various environmental conditions, and where the resizingprocessing is executed may be determined according to these conditions.

Other Embodiments

The preferred embodiments of the present invention have been explained,and the present invention can be applied to either an image distributionsystem constituted by a plurality of devices, or an image distributionapparatus consisting of a single equipment.

Note that the present invention can be achieved by directly or remotelysupplying a program that implements the functions of the aforementionedembodiments to a system or apparatus, and reading out and executing thesupplied program code by a computer of that system or apparatus. In theabove embodiments, such programs correspond to the flowcharts shown inFIGS. 3, 5, 7-8, 10-11 and 13. In this case, the form of program is notparticularly limited as long as it has a program function. Therefore,the program code itself installed in a computer to implement thefunctional processing of the present invention using the computerachieves the present invention. In this case, the form of program is notparticularly limited, and an object code, a program to be executed by aninterpreter, script data to be supplied to an OS, and the like may beused as along as they have the functions of the program.

Various recording media for supplying the program can be used. Forexample, a Floppy® disk, hard disk, optical disk, magneto-optical disk,MO, CD-ROM, CD-R, CD-RW, magnetic tape, nonvolatile memory card, ROM,DVD (DVD-ROM, DVD-R), and the like can be used.

As another program supply method, the program may be supplied byestablishing connection to a home page on the Internet using a browseron a client computer, and downloading the program from the home pageonto a recording medium such as a hard disk or the like. In this case,the program to be downloaded includes the computer program itself of thepresent invention or a compressed file including an automaticinstallation function. Also, the program code that forms the program ofthe present invention may be segmented into a plurality of files, whichmay be downloaded from different home pages. That is, the claims of thepresent invention include a WWW server which makes a plurality of usersdownload program files required to implement the functional processingof the present invention by the computer.

Also, a storage medium such as a CD-ROM or the like, which stores theencrypted program of the present invention, may be delivered to theuser. In this case, the user who has cleared a predetermined conditionmay be allowed to download key information used to decrypt the encryptedprogram from a home page via the Internet, and the program encryptedusing that key information may be installed in a computer in anexecutable form.

The present invention can be implemented in a mode other than the modefor implementing the functions of the aforementioned embodiments byexecuting the readout program code by the computer. For example, thefunctions of the aforementioned embodiments can also be implemented bysome or all of actual processing operations executed by an OS or thelike running on the computer on the basis of an instruction of thatprogram.

Furthermore, the program read out from the recording medium may bewritten in a memory of an extension board or a function extension unit,which is inserted in or connected to the computer. In this case, thefunctions of the aforementioned embodiments are implemented by some orall of actual processes executed by a CPU or the like arranged in thefunction extension board or unit.

As described above, according to the above embodiments, the load on theresizing processing in the client terminal can be reduced.

Also, deterioration of image quality due to a resizing instruction atthe client terminal can also be prevented.

By limiting a client terminal which is permitted to request resizingprocessing in the server, simultaneous requests from a plurality ofclient terminals to the server can be avoided.

Since the necessity/non-necessity of resizing processing in the serveris determined according to the amount of load of the resizing processingin the client terminal, the load on the resizing processing in theserver can be reduced, and the system load can be appropriatelydistributed.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all such modifications and equivalent structures andfunctions.

This application claims priority from Japanese Patent Applications No.2005-314844 filed Oct. 28, 2005 and Japanese Patent Applications No.2006-220639 filed Aug. 11, 2006, which are hereby incorporated byreference herein in their entirety.

1. An image distribution system for transmitting image data captured bya camera unit at a predetermined resolution from a server to a clientterminal, and displaying the image data on the client terminal, whereinthe client terminal comprises: a notification unit configured to notifythe server of size information of a window for displaying the image dataand whose size has been changed in accordance with a size changeinstruction; a display control unit configured to control to display theimage data received from the server on the window, a first resizing unitconfigured to change a display size of the image data in the clientterminal based on a size of a window for displaying the image data andthe size of which has been changed in accordance with the size changeinstruction; a first determination unit configured to determine, basedon a load state of processing in the client terminal and whether or notthe client terminal has a control right for changing the capturingdirection of the camera unit, whether or not to request the server toexecute resizing processing of the image data in accordance with thesize change instruction; and a first unit configured to, in a case thatthe first determination unit determines not to request the server toexecute the resizing processing, control the first resizing unit toresize the image data; wherein the server comprises: a second resizingunit configured to change a resolution upon capturing the image databased on the size information in response to the notification by thenotification unit, wherein the display control unit of the clientterminal receives the image data resized by the second resizing unit anddisplays the received image data on the window, in a case that the firstdetermination unit determines to request the server to execute theresizing processing, and the display control unit displays the imagedata resized by the first resizing unit on the window, in a case thatthe first determination unit determines not to request the server toexecute the resizing processing.
 2. The system according to claim 1,wherein when the first determination unit determines that the load stateof processing in the client terminal is not lower than a predeterminedload state and determines that the client terminal has the control rightfor changing the capturing direction of the camera unit, the firstdetermination unit determines to request the server to execute resizingprocessing of the image data and the notification unit notifies theserver of display size information of the changed window, and whereinwhen the first determination unit determines that the load state ofprocessing in the client terminal is lower than the predetermined loadstate or determines that the client terminal does not have the controlright changing the capturing direction of the camera unit, the firstdetermination unit determines not to request the server to executeresizing processing of the image data and the notification unit does notnotify the server of the display size information of the changed window.3. The system according to claim 1, further comprising a calculationunit configured to calculate the load state based on the size of thewindow and the resolution of the image data.
 4. The system according toclaim 1, further comprising a calculation unit configured to calculatethe load state based on frame rates before and after the changeinstruction.
 5. The system according to claim 1, further comprising: asetting unit configured to set at least one of an operation condition ofthe client terminal that receives the image data and an environmentcondition specific to the system, wherein the environment condition isrelated to the client terminal, a communication apparatus including theserver and a communication line of the system, wherein the firstdetermination unit determines based on the condition set by the settingunit whether or not to request the server to execute resizing processingof the image data corresponding to the size change instruction.
 6. Thesystem according to claim 5, wherein the operation condition isassociated with image quality upon displaying the image data in theclient terminal.
 7. The system according to claim 5, wherein theoperation condition is associated with an image frame rate upondisplaying the image data in the client terminal.
 8. The systemaccording to claim 5, wherein the operation condition is associated withrecording of the image data on a storage media of the client terminal orthe server.
 9. The system according to claim 5, wherein the operationcondition is associated with a consumption power of a communicationapparatus which forms the client terminal.
 10. The system according toclaim 5, wherein the environment condition is associated with atransmission capacity and transmission quality of the communication linethat connects the client terminal with the server.
 11. The systemaccording to claim 5, wherein the environment condition is associatedwith a performance of a communication apparatus that constitutes theclient terminal or the server.
 12. The system according to claim 1,further comprising: a second determination unit configured to determinewhether or not to cause the server to execute resizing processing of theimage data in accordance with the size change instruction, based onwhether the size of the window is enlarged or reduced; and a second unitconfigured to cause the first resizing unit to execute resizing of theimage data in a case that the second determination unit determines notto request the server to execute the resizing processing, wherein thenotification unit notifies the server of size information of the windowwhich has been changed in accordance with the size change instruction,in a case that the second determination unit determines to cause theserver to execute the resizing processing, and the display control unitcontrols to display the image data received from the server, or theimage data resized by the first resizing unit, on the window.
 13. Thesystem according to claim 1, wherein the first determination unitdetermines whether or not to request the server to execute resizingprocessing of the image data, based on the load state of processing inthe client terminal and whether or not the client terminal has thecontrol right for changing the capturing direction of the camera unitcorresponding to the image data whose size has been changed inaccordance with the size change instruction.
 14. The system according toclaim 1, wherein the server is a network camera for capturing imagedata.
 15. A client terminal for receiving image data captured by acamera unit at a predetermined resolution from a server, and displayingthe received image data on a window, comprising: a notification unitconfigured to notify the server of size information of a window whichdisplays the image data and a size of which has been changed inaccordance with a size change instruction; a display control unitconfigured to receive the image data resized by the server, anddisplaying the resized image data on the window; a resizing unitconfigured to change a display size of the image data based on the sizeof the window has been changed in accordance with the size changeinstruction; a determination unit configured to determine, in accordancewith a load state of processing of the client terminal and whether ornot the client terminal has a control right for changing the capturingdirection of the camera unit, whether or not to request the server toexecute resizing processing of the image data corresponding to the sizechange instruction; and a control unit configured to, in a case that thedetermination unit determines not to request the server to execute theresizing processing, control the resizing unit to resize the image data,wherein the notification unit notifies the server of display sizeinformation of the window which has been changed in accordance with thesize change instruction, in a case that the determination unitdetermines to request the server to execute the resizing processing, andthe display control unit displays the image data resized by the resizingunit on the window, in a case that the determination unit determines notto request the server to execute the resizing processing.
 16. Theterminal according to claim 15, wherein, when the determination unitdetermines that the load state of processing in the client terminal isnot lower than a predetermined load state and determines that the clientterminal has the control right for changing the capturing direction ofthe camera unit, the determination unit requests the server to executeresizing processing of the image data and the notification unit notifiesthe server of display size information of the changed window, andwherein when the first determination unit determines that the load stateof processing in the client terminal is lower than the predeterminedload state or determines that the client terminal does not have thecontrol right for changing the capturing direction of the camera unit,the determination unit determines not to request the server to executeresizing processing of the image data and the notification unit does notnotify the server of the display size information of the changed window.17. The terminal according to claim 15, further comprising a calculationunit configured to calculate the load state based on the size of thewindow and the resolution of the image data.
 18. The terminal accordingto claim 15, further comprising a calculation unit configured tocalculate the load state based on frame rates before and after the sizechange instruction.
 19. The client terminal according to claim 15,wherein the server is a network camera for capturing image data.
 20. Amethod of controlling an image distribution system for transmittingimage data captured by the camera unit at a predetermined resolutionfrom a server to a client terminal, and displaying the image data on theclient terminal, comprising: an input step of inputting a changeinstruction of a size of a window which displays the image data; anotification step of notifying the server of size information of thewindow the size of which has been changed in accordance with a sizechange instruction; a first resizing step of causing the server tochange a resolution upon capturing the image data based on the sizeinformation; a display control step of causing the client terminal toreceive the image data resized in the first resizing step and displayingthe resized image data on the window; a second resizing step of causingthe client terminal to change a display size of the image data based ona size of a window which has been changed in accordance with the sizechange instruction; a first determination step of determining, based ona load state of processing in the client terminal and whether or not theclient terminal has a control right for changing the capturing directionof the camera unit, whether or not to request the server to execute theresizing processing of the image data corresponding to the size changeinstruction; and a step of controlling, in a case that it is determinedin the first determination step not to request the server to execute theresizing processing, the second resizing step to cause the clientterminal to resize the image data, and in a case that it is determinedin the first determination step to request the server to execute theresizing processing, the notification step to notify the server ofinformation of the window size which has been changed in accordance withthe size change instruction, and the display control step causes theclient terminal to display the image data resized by the server.
 21. Themethod according to claim 20, wherein when it is determined in the firstdetermination step that the load state of processing in the clientterminal is not lower than a predetermined load state and that theclient terminal has the control right for changing the capturingdirection of the camera unit, it is determined in the firstdetermination step to request the server to execute resizing processingof the image data and the display size information of the changed windowis notified to the server in the notification step and, wherein when itis determined in the first determination step that the load state ofprocessing in the client terminal is lower than a predetermined loadstate or that the client terminal does not have the control right forchanging the capturing direction of the camera unit, it is determined inthe first determination step not to request the server to executeresizing processing of the image data and the display size informationof the changed window is not notified to the server.
 22. The methodaccording to claim 20, further comprising a calculation step ofcalculating the load state of the client terminal based on the size ofthe window and the resolution of the image data.
 23. The methodaccording to claim 20, further comprising a calculation step ofcalculating the load state of the client terminal based on frame ratesbefore and after the size change instruction.
 24. The method accordingto claim 20, further comprising: a setting step of setting at least oneof an operation condition of the client terminal that receives the imagedata and an environment condition specific to the system, wherein theenvironment condition is related to the client terminal, a communicationapparatus including the server and a communication line of the system,wherein it is determined in the first determination step based on thecondition set in the setting step whether to request the server toexecute the resizing processing of the image data corresponding to thesize change instruction, or to cause the client terminal to execute theresizing processing in the second resizing step.
 25. The methodaccording to claim 20, further comprising: a second determination stepof determining, depending on whether the size of the window is enlargedor reduced in the input step, whether or not to request the server toexecute resizing processing of the image data corresponding to the sizechange instruction; and a step of controlling, in a case that it isdetermined in the second determination step not to request the server toexecute the resizing processing, the second resizing step to resize theimage data, wherein in a case that it is determined in the seconddetermination step to request the server to execute the resizingprocessing, the notification step notifies the server of information ofthe window size which has been changed in accordance with the sizechange instruction, and in the display control step, the image dataresized by the server or the image data resized in the second resizingstep is displayed on the window.
 26. The method according to claim 20,wherein the server is a network camera for capturing image data.
 27. Animage distribution system for transmitting image data captured by acamera unit at a predetermined resolution from a server to a clientterminal, and displaying the image on the client terminal, wherein theclient terminal comprises: a notification unit configured to notify theserver of size information of a window for displaying the image andwhose size has been changed in accordance with a size changeinstruction; a display control unit configured to control to display animage on the window in accordance with image data from the server on thewindow, a first resizing unit configured to change a display size of theimage in the client terminal based on a size of a window for displayingthe image and the size of which has been changed in accordance with thesize change instruction; a determination unit configured to determine,based on whether or not the client terminal has a control right forchanging the capturing direction of the camera unit corresponding to theimage whose size has been changed in accordance with the size changeinstruction, whether or not to request the server to execute resizingprocessing of the image data in accordance with the size changeinstruction; and a control unit configured to, in a case that thedetermination unit determines not to request the server to execute theresizing processing, control the first resizing unit to resize the imagedata; wherein the server comprises: a second resizing unit configured tochange a resolution upon capturing the image data based on the sizeinformation in response to the notification by the notification unit,wherein the display control unit of the client terminal receives theimage data resized by the second resizing unit and displays the image onthe window according to the received image data, in a case that thedetermination unit determines to request the server to execute theresizing processing, and the display control unit displays the image onthe window according to the image data resized by the first resizingunit, in a case that the determination unit determines not to requestthe server to execute the resizing processing.
 28. The system accordingto claim 27, wherein the display control unit controls to display pluralimages on the window in accordance with image data from plural servers,each of the plural servers having a camera unit, the determination unitdetermines, based on whether or not the client terminal has the controlright for changing the capturing direction of each of the plural cameraunits, whether or not to request each of the plural servers to executeresizing processing of the image data corresponding to each of theplural servers, in accordance with the size change instruction; thefirst resizing unit changes a display size of an image corresponding tothe image data from a server which is determined by the determinationunit not to request to execute resizing processing, the display controlunit of the client terminal receives the image data resized by the firstresizing unit and displays the image in accordance with the receivedimage data on the window, and the display control unit of the clientterminal receives image data resized by the second resizing unit of aserver which is determined by the determination unit to request toexecute resizing processing, and displays an image in accordance withthe received image data on the window.
 29. The system according to claim27, wherein the server is a network camera for capturing image data. 30.A client terminal for receiving image data captured by a camera unit ata predetermined resolution from a server, and displaying the receivedimage data on a window, comprising: a notification unit configured tonotify the server of size information of a window for displaying theimage data and whose size has been changed in accordance with a sizechange instruction; a display control unit configured to control todisplay the image on the window in accordance with the image data fromthe server; a resizing unit configured to change a display size of theimage based on a size of a window has been changed in accordance withthe size change instruction; a determination unit configured todetermine, based on whether or not the client terminal has a controlright for changing the capturing direction of the camera unitcorresponding to the image data whose size has been changed inaccordance with the size change instruction, whether or not to requestthe server to execute resizing processing of the image data inaccordance with the size change instruction; a control unit configuredto, in a case that the determination unit determines not to request theserver to execute the resizing processing, control the first resizingunit to resize the image data, wherein the notification unit notifiesthe server of display size information of the window which has beenchanged in accordance with the size change instruction, in a case thatthe determination unit determines to request the server to execute theresizing processing, and the display control unit displays the image onthe window in accordance with the image data resized by the resizingunit, in a case that the determination unit determines not to requestthe server to execute the resizing processing.
 31. The client terminalaccording to claim 30, wherein the display control unit controls todisplay plural images on the window in accordance with image data fromplural servers, each of the plural servers having a camera unit, thedetermination unit determines, based on whether or not the clientterminal has the control right for changing the capturing direction ofeach of the plural camera units, whether or not to request each of theplural servers to execute resizing processing of the image data inaccordance with the size change instruction for changing the size of thewindow for displaying the plural images, the resizing unit changes adisplay size of images corresponding to the image data from the pluralservers, in a case that the determination unit determines not to requestthe each of the plural servers to execute resizing processing, thedisplay control unit of the client terminal receives the image dataresized by the resizing unit and displays the image in accordance withthe received image data on the window, and the notification unitnotifies a server which is determined by the determination unit torequest to execute resizing processing, display size information of thewindow whose size has been changed in accordance with the size changeinstruction.